This invention is a valve assembly located at a hull penetration of a submarine including a hull valve and a backup valve. Such a valve functions to control liquids passing through the hull of a submarine and comprises two valves in series, one serving as a backup in case the other fails. The valve assembly permits the intake and/or discharge of seawater or other fluids for use by various systems, such as the submarine's cooling system. Because the valve internals are exposed to seawater, corrosion resistance is critical.
The prior art hull and backup valves include a large hull insert made of a steel alloy welded in to the hull. The hull and backup valves are attached to the hull insert with large attachment studs and nuts. The flow path of the prior art valves extends perpendicular to the hull surface and then bends at a right angle so as to be parallel to the hull surface. Two valves are positioned in the line along either the section of the flow path parallel to the hull surface or the section of the flow path perpendicular to the hull surface. The splined valve stem is typically made of a Ni-Cu alloy sold by Inco Alloys International under the trademark K-MONEL and is connected to the actuator via a pinion gear. The bonnet is typically secured in place with cap screws or studs. The larger valves, i.e., greater than 6 inches NPS (nominal pipe size), include a welded overlay on the internal surfaces to improve corrosion resistance. In the smaller valves, however, the physical dimensions impede the welding of such an overlay.
The prior art has several disadvantages. The valves tend to be very large and heavy due to the large attachment studs and nuts required to withstand underwater explosions. The hull insert adds additional weight and decreases the available internal volume of the ship. To perform any kind of maintenance other than external inspection generally requires the valve to be removed from the hull and reworked in the shop. Removing these overly large hull and backup valves frequently requires that nearby components and piping be removed first. Since these prior art valves in the smaller sizes do not have adequate corrosion resistance in key areas, they require extensive rework and repair. Finally, little attention has been given to reducing the internal hull volume and weight of the hull and backup valve and the associated hull insert. As the hydraulic actuators of the older valves are add on components, the designs have merely incorporated the hydraulic actuators and associated equipment into the existing designs in lieu of being integrally designed with the valve. Integral actuator designs result in large volume and weight improvements.